Burner control apparatus and system



Aug. 14, 1934. H DEVER 1,969,967

BURNER CONTROL APPARATUS AND SYSTEM Filed Aug. 5, 1929 2 Sheets-Sheet 1 Aug. 14, 1934. H. F. DEVER BURNER CONTROL APPARATUS ;AND SYSTEM Filed Aug. 5. 1929 2 Sheets-Sheet 2 flW/WF D6145)? I I a I Patented Aug. 14, 1934 UNITED STAT-ES PATENT oFF cE Henry F. Dover, Elkhart, lndL, assignor, by means assignments, to Minneapolis-Honeywell lator Company, Minneapolis, Mimn, a corporation of Delaware Application August 5, 1929, Serial No. 383,728

33 Claims.

This invention relates to burner control apparatus and systems and has particular relation to electrical devices and circuits for controlling the operation of oil burners and the like.

The primary object of the invention is to provide new and improved apparatus and circuits for controlling the operation of oil burner systems or the like in accordance with conditions of corn! bustion in such systems. i

A specific object of the invention is to provide apparatus and circuits for controlling the ignition and fuel supply means of an oil burning system or the like in accordance with conditions of combustion in such system.

A further object of the invention is to, provide apparatus and circuits for controlling systems of the above indicated character in such manner that, upon a failure of combustion, the fuel supplying apparatus of the system will be' rendered inoperable for a predetermined interval of time,

w'hereaiter an attempt to re-establish combustion will be made by re-energizing the fuel supplying and ignition apparatus, this attempt being made without sacrificing the desired features of safety whereby continued operation of the fuel supplying means is prevented if combustion fails to be established.

Other objects and advantages of the invention will appear from a consideration of the iollowing detailed description taken in connection with the accompanying drawings, in which:

Figure 1 is a front elevational view of a. control device designed and constructed in accordance with the invention, the coverof the casing 35 for such device being removed;

Fig. 2 is a vertical sectional view taken on the line 22 of Figure 1, with the cover of the casing in place; I

Fig. 3 is a fragmentary view, partly in front elevation and partly in vertical section, taken on the line 3-3otFig. 2;

Fig. 4 is a diagrammatic representation of an oil burner system or the like embodying the control device shown in Figs. 1, 2 and 3 connected in circuit relation to certain other devices comprising all of the other essential controlling elements of such a system; v

Fig. 5 is a simplified schematic representation of the electrical circuits and devices shown in Fig. 4.

Referring to the drawings, the control device shown in Figs. 1, 2 and 3 comprises a suitable housing or casing 11 within which the operative Y parts of the device are disposed, as will presently 55 appear. A sleeve member 12 projects rearwardly from the rear wall of the casing 11, to which said sleeve is secured by means of screws 13 extending through suitable apertures or slots in an annular flange portion 12a of said sleeve, and also through corresponding openings in the rear wall of the casing 11. Nuts 14 cooperate with the screws 13 to secure the sleeve member 12 in the position shown. The rear extremity of the sleeve member 12 has a protruding portion 12b to which the forward extremity of a coiled bi-metallic or other 65 thermostatic element 15 is secured by means of a screw 16. The rear extremity of thethermostatic element15 is secured between nuts 17 and 18 on the screw-threaded extremity of an angularly. bent portion 19a of a rod or spindle 19 extending 7 axially of the thermostatic element 15 and the sleeve 12 and through a suitable opening in the rear wall of the casing 11.

The forward extremity of the rod or spindle 19, which projects into the interior of the casing 7 '11, is screw-threaded for substantially the entire length of said portion and a pair of nuts 20 are placed in mutually locking relation on this screw threaded portion near the rear wall of the casing 11. A cup-shaped metallic friction 8 washer 21 is placed on the forward extremity of the rod 19 with the, lip portions thereof overlying the nuts 20 as shown. A similar cupshaped washer 22 is placedin opposing relation to the washer 21 and between these two washers 35 a switch-carrying arm 23 is disposed, this arm being apertured to permit the rod 19 to extend therethrough in freely rotatable relation. A third cup-shaped'washer 24 is placed on the forward extremity of the arm 19 in opposed relation to the washer 22 and between the two washers 22 and 24 a coileolv compression spring 25 is disposed around the rod 19. Flat friction washers. 26 and 2'! are disposed between the innor surfaces of the cupped washers 22 and 24,

'- respectively, and the corresponding extremities of the spring 25. The parts'21, 22, 23, 24, 25, 26 A and 27 are held longitudinally of the rod 19 in the positions shown,\by the locked nuts 20 and a similar pair of locked nuts 28 that are located on the screw threaded foremost portion of the rod 19 immediately in front of the cupped washer 24. v 1

Another cupped washer 29 is positioned on the rod 19 in front of the locked nuts 28 and with its lip portions overlying said nuts. Another such I cupped washer 30 is placed on the rod 19 in opposed relation to the washer 29 and between these two washers 29 and 30 a second switch-carrying arm 31 is placedon the rod 19 in a mariner no similar to that inwhich the switch-carrying arm 23 is so disposed, that is, with the rod 19 extending through a suitable aperture in said switch arm in freely rotatable relation thereto. Still another cupped washer 32 is placed on the rod 19 with the lip portions thereof facing rearwardly in opposed relation to the washer 30 and between the two washers 30 and 32 a second coiled compression spring 33 is disposed around the rod 19. Between the inner facesof the cupped washers 30 and 32 respectively, and the corresponding extremities of the spring 33, flat friction washers 34 and 35 are disposed. The

parts 29, 30, 31, 32, 33, 34 and 35 are held inposition longitudinally ,of the rod 19 between the locked nuts 28 and a nut 36 that is screwed onto the forward extremity of the rod 19 in front of the cupped washer 32. The foremost extremity of the rod 19 is flattened or mutilated as indicated at 37 to prevent the nut 36 from coming off by reason of vibration or other causes.

With the above described construction-it will be seen that the switch-carrying arm 23 is pressed between the fiat outer surfaces of the cupped washers 21 and 22 by means of the spring 25 and that the switch-carrying arm 31 is similarly pressed between the washers 29 and 30 by means of the spring 33. This method of holding the arms 23 and 31 provides a frictional slip connection between the rod 19 and each of said arms whereby said arms will be rotated in accordance with the rotation of the rod or spindle 19 as long as such movement of the arms is unrestrained. When such movement is restrained, however, the rod 19 is permittedto rotate freely without imparting any further movement to the switchcarrying arms. The structural details of the frictional slip connections, as herein described do not constitute a part of the present invention but are described herein because these frictional connections are utilized in combination with certain other elements as will hereinafter appear.

The rearward switch-carrying arm 23 has secured thereto a clip 38 which embraces the tubular container of a mercury electric contactor 39 whereby said contactor may be tilted in accordance with the rotative movement of the arm 23. The container of this contactor 39 is of curved or humped formation, as shown in Fig. 3, for a purpose which will appear hereinafter. By reason of the curved formation of the container of the contactor 39, it is preferable to provide a section of soft rubber tubing 40 or the like around said container and between the latter and the clip 38. The contactor 39 comprises a pair of electrodes 39a that are disposed in the left-hand extremity of the container fdrsaid contactor as the later is viewed from the front, as shown. A'body of mercury 39bis also "disposed within the container of this contactor and is adapted to be moved between the extremities of said container to make and break the electrical circuit between the electrodes 39a in accordance with the angle .of inclination of the container.

Two insulated flexible conductors 41 and 42 are individually connected to the two electrodes 39a of the .contactor 39 and extend therefrom to terminal posts 43 and 44, respectively, located on a terminal board 45 which is made of insulating material and which is secured within the casing 11 by means of bracket members 46 and 47 and cooperating screws 48 and 49, respectively. The bracket members46 and 47respectively project inwardly from flat securing portions 46a and 47a which are secured to the inner surfaces of sidewalls 11b and 110 of the casing 11 by rivets 50 or other suitable means. The forward extremities of the portions 46a and 47a of the bracket members 46 and 47 are bent inwardly to form ear portions 46b and 47b hav ing screw-threaded openings therein for the reception of screws 51 and 52 which are adapted to pass through corresponding openings in a cover.

member 53 for the casing 11 which is shown in its normal position with respect to said casing in Fig. 2. The bracket members 46 and 47 also preferably comprise portions extending rearwardly and bent inwardly at their rearmost extremities to form another pair of bracket portions 46c and 470 which may be utilized, if desired, to secure the terminal board 45 in a different position within the casing 11.

The forward switch-carrying arm 31 has secured thereto a clip 54 embracing the container of a mercury electric contactor 55 which has a pair of electrodes 55a disposed in the right-hand extremity thereof for cooperation with a body of mercury 55b which is also disposed within the container of said contactor. Twoinsulated flexible conductors 56 and 57 are individually connected to the two electrodes 55a of the contactor 55 and respectively extend therefrom to the terminal post 44 on the terminal board 45 and to another terminal post 58 on said terminal board.

It will be seen, therefore, that one electrode of the contactor 39 and one electrode of the contactor 55 are electrically connected together, since the conductors 42 and 56 are connected to the common terminal post 44.

The terminal posts 43, 44 and 5B are provided for receiving the connecting leads of the two contactors 39 and 55 and the external connections to said contactors are adapted to be made through terminalposts 59, 60 and 61 which are respectively connected to terminal posts 43, 44 and 58. The internal connections between the twosets of terminal posts are made by conducting straps 62 which are preferably constituted by metallic inserts molded into the insulating material of the terminal board 45 as shown in Fig. 2. The front face of the terminal board 45 is preferably provided with integral forwardlyprojecting portions 63 which serve as partitions between the several terminal posts to prevent accidental short circuiting therebetween. The external connections for the contactors 39 and 55 may be made by means of conductors entering the-casing 11 through suitable apertures which may be readily made by removing either or both of two knockout portions 64 and 65 which are respectively provided in the side walls 11b and 11c of the casing in the space below the terminal board 45.

The thermostatic element 15 is adapted to be disposed within the stack or flue for conducting the gaseous-products of combustion away from the combustion chamber of the heating system to be controlled, and for this purpose a securing member 66 is provided, which comprises a sleeve portion 66a surrounding the sleeve member 12 and having a bore-of such diameter as to be freely 'slidable over said sleeve member 12. A boss porber 66 surrounds the sleeve portion 660: at an intermediate point thereof and is suitably aper-.

tured as indicated at 6611 to receive bolts or screws for securing the member 66 to the wall of the stack or flue. Since such stacks or fiues are ordinarily made of metal of cylindrical formation, the flange portion 66a is preferably curved as indicated in Fig. 2 to conform to the external surfaces of such stacks or flues.

The entire device as above described is mounted on the outside of the stack in a manner which will be readily apparent, namely, by cutting a suitable hole in a wall of the stack through which the thermostatic member 15 and the part of the sleeve portion 66a. behind the flange portion 660 may extend. The device is then placed in this position and suitable securing means are passed through the apertures 66d and corresponding holes which will have been provided in the wall of the stack around the main opening for receiving the partsv 15 and 66a. When the device is so mounted the entire assembly, with the exception of the member 66 and set-screws 67, may be rotated within the sleeve portion 66a until the casing 11 is properly leveled, and may also be movedaxially of the sleeve 66a to secure the proper position of the thermostatic member 15 within the stack, whereafter the set-screw 67 may be tightened to hold the device securely in the position desired.

The sleeve member 12 is'preferably apertured V as indicated at 120 to permit a certain amount of cold air to be drawn through the inside of said sleeve member for the purpose of ventilating or cooling the thermostatic member 15. The amount of air drawn in through the aperture 120 by reason of the draft inside the stack may be regulated by sliding the sleeve member 12inwardly or outwardly within the sleeve portion 660 of the securing member'66 until the desired cooling effect of the thermostatic member 15 is obtained, since the forward extremity of the sleeve portion 660 is thus caused to overlap a greater or less portion of the aperture 120.

This regulation or adjustment is so made that the thermostatic member 15 responds in the desired manner to the conditions of combustion within the combustion chamber of the heating system, which response isv eifected by reason of the expansion and contraction of the member 15 in accordance with the temperature of the gaseous products of combustion thatare being conducted away from said combustion chamber through the stack or fine within which said member 15 is disposed. The construction of the sleeve member 12 with the aperture 120 therein, whereby the abovedescribed regulation or adjustment may be effected, does not constitute a part of the present invention and'therefore this feature is not claimed herein. F

It will be seen that as the thermostatic member 15 expands and contracts in response to changes of temperature within the stack or flue, the rearmost extremity thereof will be rotated and this rotation will be transmitted directly to the rod 19. The corresponding rotative movements of this rod are imparted to the contactors 39 and 55v through the heretofore described frictional slip connections between the rod 19 andv the carrying members 23'and 31, respectively, for said con: t actors.

When the thermostatic member 15 is relatively cool, asyfor example, after a substantial period of inactivity of the heating system, or, in other words, after the termination of a period of combustion, this thermostatic member is in a condition which results in the contactors 39 and 55 occupying the positions shown in the drawings. This means that the rearward extremities of the member 15 and the rod 19 have been turned to their extreme positions in a counter-clockwise direction, as viewed in Figs. 1 and 3, and that the carrying members 23 and 31 for the contactors 39 and 55 have been likewise turned in the same direction. The extreme positions of the members 23 and 31 in this direction are limited by engagement of both of said arms with a stop member or pin 68 that is suitably secured in the rear Wall 1111 of the casing 11 and projects forwardly from said wall within the casing a suiiicient distance to arrest the movements of said arms.

Under the conditions illustrated it will be seen that the bodies of mercury within the contactors 39 and 55 will have flowed to the left-hand extremities of the containers of these contactors, since each of these containers is then tilted downwardly to the left, as shown. The electrodes 39a of the contactor 39 are therefore in electrically connected relation to complete the circuit between the conductors 41 and-42, which are respectively connected through .the terminal posts 43 and 44 to the terminal posts 59 and 60, as heretofore described. The electrodes 55a of the con tactor 55, however, are disconnected from each other and the circuit between the conductors 56 and 57 is therefore interrupted at this point.

When the temperature of the thermostatic member 15 is increased, as in response to the establishment of combustion in theheating system, the resultant movement of this member causes the rod or spindle 19 to be rotated in a clockwise direction, as viewed in Figs. 1 and 3', with the result that the contactors 39 and 55 are similarly moved toward the positions in which the containers of said contactors are tilted in the reverse direction of that shown. In a relatively short time after such movement of the members 15 and 19 and the contactors 39'and 55, the latter contactor attains a position in which its inclination is reversed so that the body of mercury therein flows to the opposite end of the container and completes the electrical circuit between the electrodes 55a. The result accomplished by the making of this circuit will appear hereinafter in the description of the system shown in Figs. 4 and 5.

Shortly after the contactor 55 has been actuated tofithe position in which its circuit is closed,

the upper extremity of the switch-carrying arm 31 for said contactor engages a stop member or pin 69, which projects forwardly within the cas ing 11 from the rear wall 110, thereof in a manner similar to that described with respect to the stop pin 68. It may be noted, however, that since the pin 68 is adapted to occupy one position only it projects through the rear wallof the casing. It

is desired, however, that the other extreme position of the contactor 55 may be adjustably limited and for this reason the stop pin 69 is removably held in place, as by means of a screw or screwthreaded portion which is adapted to extend through any one of severalholes- 70in the rear wall 11a of the casing 11. After the upper extremity of the carrying arm 31 engages the stop pin 69 in any one of its several possible positions,

further movement of said arm and of the con-- tactor 55 carried thereby is precluded, but continued rotation of the rod 19 in a clockwise direction in response to further heating of the thermostatic member 15 is readily permitted by reason of the frictional slip connection between the rod 19 and the arm 31.

During the above-described movement of the contactor 55 in accordance with the rotation of the rod 19, the other contactor 39 partakes of similar movement, but owing to the curved formation of the container for this latter contactor the body of mercury therein does not move to the right-hand extremity of said container as soon as such movement takes place within the contactor 55. It is necessary, therefore, that the contactor 39 be permitted to move a substantial distance beyond the position which it occupies when the body of mercury within the contactor 55 flows to the right-hand extremity of the contrainer for said contactor. Also, the extreme right-hand or clockwise position of the contactor 39 is ordinarily considerably beyond, that of the contactor 55, but whether ornot this is the case, it is desired that this extreme position of the contactor 39 be adjustable independently of the extreme position of the contactor 55. Accordingly, a separate stop member 71 is provided for limiting the extreme clockwise position of the contactor 39. This member 71 is in the form of ;a nut engaging the screw-threaded shank of a screw. 72, which shank isextended through an 'arcuate slot '73 in the'rear wall 11a of the casing 11, with the head of said screw '72 engaging the rear surfaces of said wall along the sides of said slot. The stop nut 71 extends forwardly a sumcient distance to be engaged by the upper extremity of the 8.1:111 23 which carries the contactor 39 and therefore the extreme clockwise position of this arm and contactor is limited to a position in which said arm engages said stop nut. It will be apparent that this position may be adjusted as desired by loosening the nut 71 on the screw 72 "and moving these two elements to the desired position along the slot 73, where the nut 71 may again be tightened. v

When movement of both of the arms 31 and 23 has been arrested by engagement between these arms and the stop members -69 and 71, respectively, the rod 19 is still permitted to be rotated freely in a clockwise direction, as viewed in Figs. 1 and 3, because the arm 23, as well as the arm 31, is provided with a frictional slip connection with the rod or spindle 19. Such movement of the rod 19 will continue as. long as the temperature of the thermostatic member 15 continues to rise. When this rise in temperature stops, the rotation of the rod 19 is likewise stopped and as soon as this temperature starts to fall in response to termination or failure of combustion, the rod 19 begins to turn in the reverse direction. By reason of the two frictional slip connections heretofore described, the reverse movement of both of the contactors 39 and 55 also begins immediately; This immediate reversed movement of the contactors 39 and 55 upon a drop in the temperature of the member 15 is a very important result following from the use of the two frictionaLslip connections. It is during this reverse movement that the curved formation of the container-of the contactor 39 performs its essential function, which is to delay thereclosing of the circuit between the electrodes 39a of said contactor. The extent of this delay is determined by the position of the stop member 71 which, as previously stated,

determines the extreme clockwise position of the arm 23 and the contactor 39 that is carried thereby. In any event, the interval of this delay is of substantial duration after the time when the circuit between the electrodes 55a of the contactor 55 is broken by reason of the reversal in the inclination of the latter contactor, which heating system to be stopped. The substantial interval of time between the stopping of this op-.

eration and the reclosing of the circuit through the contactor 39 is made amply sufficient to allow the combustion chamber of the heating system to be ventirelypurged of the highly inflammable or explosive gases which may remain in said combustion chamber at the instant that the actual combustion ceases.

When the combustion chamber has been purged of this matter, it is desirable that the operation of the fuel supplying means and of the ignition means of the system be resumed in an attempt to re-establish combustion where the latter was in- V terrupted otherwise than in response to the normal conditions requiring complete shut-down of the system. It will appearhereafter in connection with the description of Figs. 4 and 5 that the device including the contactors 39 and 55 causes such attempt at re-establishment of combustion to be made in every case where combustion was interrupted in other than a normal shut-down manner. If combustion is re-established following such an abnormal failure thereof, the contactors 39 and 55 resume their normal operating positions and so remain until combustion is again terminated. Inthe event that the apparatus fails to re-establish combustion, a safety device described hereinafter functions to lock the system entirely out of operation until manual restoration of such safety device following an' inspection of the system and correction of the abnormal condition which madegit impossible for combustion to be maintained. 'During this locked-out condition, and also during the normal periods of inactivity of the heating system, the thermostatic member 15 is relatively cool and the contactors 39 and 55 bccupy the positions corresponding to this condition, which are the positions in which these contactors are shown in the drawings.

Referring now to Figs. 4 and 5, the device shown in Figs. 1, 2 and 3 and above described with reference to said figures, is designated generally by .the reference character '74 and is mounted on the I side of a stack '75 which is adapted to conduct the gaseous products of combustion away from the combustion chamber within a furnace 76; Fuel is supplied to the furnace 76 by a pump or blower 77 operated by a motor 78,. and a device for igniting such fuel to establish combustion within said combustion chamber is indicated at\79. This latter device may be constituted by either an ignition coil having its high tension terminals connected to a suitable spark gap within the combustion chamber, or an electromagnetically-controlled valve for expanding a gas pilot fiame, or by any other shown as being associated with the boiler oi the furnace 76 and may be of any suitable well known type for controlling the system in accordance with the temperature or pressure of such boiler. The devices 74, 89 and 81 cooperate to control the operation of the heating system through the instrumentality of another control device 82 which embodies a mercury electric contactor 83 or other suitable switch for controlling the energization of the motor 78.

The contactor 83 issuitably carried by an arm 84 that is pivotally mounted at 85, and the angle of inclination of said contactor, which inclination controls the opening and closing of the circuit therethrough, is controlled by two solenoid coils 86 and 87 respectively having core members 88 and 89 pivotally connected to the arm 84 at 90 and 91. When neither of thecoils 86 and 87 is energized, the arm 84 is maintained against a suitable stop 92, as shown, by the action' of gravity on said arm and on the core members 88 and 89-. In this position the contactor 83 is tilted downwardly to the right, and, since the electrodes of this'contactor are located in the left-hand end of the container therefor, the circuit between said electrodes is interrupted. v

The solenoid coil 88 is designated as the pull coil because it is so designed that energization thereof will exert sufiicient attraction upon its core member 88 to actuate the arm 84 upwardly whereby the inclination of the contactor 83 is reversed and a circuit is completed between the electrodes of said contactor? The coil 87 is designated as the hold coil because it is so designed that energization thereof will maintain the arm 84 in raised position with the contactor 83 closed after said arm and contactor have been initially actuated by the pull coil 86. The magnetic efiect of the coil 87 is not suihcient, however, to effect initial actuation of the arm 84 to close the contactor 83.

A thermal cut-out device is embodied in the control device 82 for the purpose of efiecting a desired feature of safety in the operation of the heating system and comprises a bimetallic or other thermostatic element 93 that is freely pivoted at 94. The thermostatic member 93 is adjust'ably supported by a thumb screw 95 carried by a suitable fixed bracket member 96. The freeright-hand extremity of the thermostatic member 93 carries an electrical contacting device 97, which is preferably of the mercury electric con- 'tactor type as shown, embodied in a container comprising a well portion 97a at its right-hand extremity for a purpose hereinafter described. An electrical heating element or coil 98 is disposed around or adjacent the thermostatic member 93 for the purpose of heating said element to deflect the same in a desired manner in accordance with the length of time during which current is permitted to traverse the circuit in which said heating element or coil is connected.

The thermostatic member 93 is so designed that an increase in the temperature thereof causes its free right-hand extremity to be deflected downwardly, and a predetermined degree of such deflection results in the contactor 97 being-so inclined that the body of mercury therein flows into the well 97a to interrupt the circuit between the electrodes of said contactor, which are located in the left-hand end of the container as said cut-out has been manually restored. It is for the purpose of accomplishing this result that the container of the contactor 97 is provided with the well portion 97a, because when the body of mercury within said container hasbeen caused to flow into said well in response to-the predetermined abnormal condition, it will remain there after the thermostatic member 93 has returned to its normal position and until the contactor 97 has been further inclined downwardly to the left, which is accomplished by manually raising the free right-hand extremity of the thermostatic member 93, during which movement said member moves freely about the pivot 94. When the member 93.and the contactor 97 are manipulated in this manner, the body of mercury within the container of said contactor is caused to return to the left-hand extremity of said container to reestablish the circuit between the two electrodes located at said extremity.

The circuit connections of the apparatus above described include two supply conductors 99 and 100 which supply energy to the system from any nected through a branch conductor-103 to the othersupply conductor 100, thus completing the energizing circuit for the motor .78. i

The terminal of the contactor 97 opposite that to which the conductor 99 is connectedis also connected through a conductor 104 to one terminal of the switch or contactor of the room thermostatic device 80. The other terminal of the switch or contactor of the room thermostatic device 80 is connected through a conductor 105 to one terminal of the switcher contactor of the secondary control device 81, the other terminal of which latter switch or contactor is connected through a conductor 106 to the terminal post 60 of the control device 74. It will be remembered that this terminal post 60 is connected in common to one terminal of each of the contactors 39 and 55 of the device 74. The other terminal of the contactor 39 is connected through the terminal post 59 and a conductor 107 to one terminal of the ignition device '79, the otherterminal of which ignition device is connected directly to the other supply conductor 100. A branch conductor 108 extends from the conductor 107 to one terminal of the electrical heating element 98 of the thermal cut-out embodied in the control device 82, and the other terminal of said heating element 98 is connected through a conductor 109 to one terminal of the pull coil 86. The opposite terminal of this pull coil, as well as one terminal of the hold coil 87, is connected to the other supply conductor 100 through a branch conductor 110. The terminal of the contactor 55 other than the one which is connected in common to one terminal of the contactor 39, as above described, is connected through the terminal post 61 and a conductor 11 1 to the remaining terminal of the hold coil 87, thus completing the energizing circuit of said ance with the temperature of the space to be heated through the instrumentality of the room thermostat 80, the secondary control device 81 being normally in a condition to permit the control circuit to be completed therethrough. Assuming a condition in which the parts of the control device '74 occupy the positions indicated, which condition is that existing after a period of inactivity of the heating system, a demand for heat'in the room or other space to be heated will be evidenced by closing of the'switch or contactor embodied in the room thermostatic device 80.

The closing of this switch or contactor completes the'energizing circuits for the ignition device 79 and for the pull coil 86, since all of the switches connected in series with these devices between the supply conductors 99 and 100, namely, the switches 97, 80, 81 and 39, are then closed. Accordingly, the ignition device 79 establishes the ignition flame or spark and at the same time the contactor 83 is closed in response to the energization of the pull coil 86. The closure of the contactor 83 completes the energizing circuit of the motor 78 and thereupon said motor initiates the operation of the fuel supplying means 77. In the absence of abnormal conditions, therefore, ignitable fuel will be supplied to the combustion chamber of the furnace 76 and will there be ignited because of the energization of the ignition device 79.

If combustion is'properly established in'this manner, the hot gaseous products of combustion which will be conducted away through the stack or flue 75 will so raise the temperature of the thermostatic element 15 of the control device 7,4 that the heretofore described clockwise movement of the contactors 39 and 55 will be initiated. Continued normal operation of the system will cause the temperature of the thermostatic member 15 to be raised to such a point that the contactor 55 will be closed to complete the energizing circuit of the hold coil 87, which thereafter will maintain the motor switch or contactor 83 closed. A short time after this operation takes place, the contactor 39 is opened to de-energize the ignition device-79 and the pull coil 86, continued energization of thesedevices beingno longer required. The contactor 55 will then remain closed and the contactor 39 willremain open as long as combustion continues, If such combustion continues until the temperature of the space to be heated is raised as much as is desired, the room thermostatic device 80 will open its switch or contactor to de-energize the control circuit including the hold coil 8'7 and thereupon the motor switch 83 will be permitted to open to de-energize the motor 78 and consequently to terminate the operation of the heating system in the normal shut-down manner.

rn the event that combustion is not properly established in response to the closure of the switch or contactor of the room thermostatic device 80, the ignition device 79 and the pull coil 88 will remain energized for an unduelength of time. It will be observed that the heating element 98 for the thermostatic member 93 is connected; in series with the pull coil 86 and that,

therefore, said heating element is energized whenever the pull coiLis energized. This heating element is so designed that after a predetermined period of energization thereof, the switch or contactor 97 will be opened in the manner heretofore described. The opening of this switch or contactor disconnects all of the operating and control devices of the system from the supply conductor 99 and therefore precludes any further operation of the system until said switch or contactor is manually restored to its closed position. The thermal cut-out device embodying the thermostatic member 93, the switch or contactor 97 and the heating element 98 therefore affords complete protection to the system against the hazardous condition which would arise if operation of the fuel supplying means '77 were permitted to continue after combustion failed to be established within a reasonable interval of time.

The thermal cut-out device referred to also affords the same degree of protection in precluding operation of the fuel supplying means for an. undue length of time following a possible failure of combustion after the same is initially established, but the control device 74 cooperates with100 said thermal cut-out under such conditions to provide a further advantageous feature of operation which-has been previously mentioned. This feature is the attempt to re-establish combustion a predetermined interval of time after the same has failed following proper initial establishment thereof. This interval of time before the attempt to reestablish combustion is obtained by reason of the time delay in the reclosing of the contactor 39, which time delayresults from the curved or humped formation of the container for said conta'ctor as previously described.

It will now be seen that the opening of the contactor 55, almost immediately following a decrease r in' temperatureof the thermostatic element 15 of -pull coil 88 has been re-energized and the re-,

energizatlon of the said pull coil cannot occur until the contactor 39 has been reclosed after the desired predetermined interval of time. When the contactor 39 is thus reclosed, the pulL coil 86 is again energized and the ignition device 79 is likewise re-energized to cause the operation of the fuel supplying means and the ignition means to be restarted. If combustion is successfully re-established, the same events will occur as in the normal initiation of operation of the system, but if it is not established, the thermal cut-out device .will function also in its normal manner to open the switch or contactor 97 whereby the heating system is locked entirely out of operation until said switch or contactor 97 is manually restored to its closed position.

From a consideration of the above description of operation of the system it will appear that every abnormal failure of combustion, after proper initial establishment thereof, will result 1 5- meager thermostatic element 15 of the control device 74. During this interval of time the combustion chamber is entirely purged of the highly inflammable or explosive gases which may be present for a few moments immediately following extinguishment of the flame in the combustion chamber. It has already been pointed out that the provision of this interval of time before an attempt to re-establish combustion can be made, constitutes the major feature of the present invention, and it will be seen that the provision of this interval of time is made possible by reason of the novel features of construction of the control device designated generally by the reference character '74, these novel features residing in the provision of two separate frictional slip connections, or the equivalent thereof, between the thermostatic actuator of said device 74 and'the two con'tactors 39 and 55, respectively, which are actuated thereby.

It is to be noted that the operations of attempting to re-establish combustion are performed only when combustion has been terminated or interrupted in an abnormal manner, as

I the termination of combustion in a normal manher in response to the opening of either of the switches or contactors of the devices and 81 interrupts the energizing circuits for the ignition device 79 and thepull coil 86, as well as that for the hold coil 87, so that under these conditions the motor switch or contactor 83 is not reclosed when the contactor 39 normally returns to its closed position. i

While only one specific embodiment of the present invention, in respect to both details of structure and circuit connections has been disclosed herein, it will be apparent to those skilled in the art that many changes and modifications may be made in such structural details and circuit connections without departing from the spirit and scope of the invention as set forth in the appended claims.

Having thus described this specific embodiment of the invention, what is claimed as new and is desired to secure by Letters Patent is:

1. In a heating control system, in combination, a combustion chamber, means for supplying fuel thereto, an electric motor for operating said fuelsupplying means, electrically operable means for igniting the fuel supplied to said combustion chamber, a switch for controlling the energization' of said motor, means for closing said motor switch, means for maintaining said motor switch closed, and a device for controlling said closing means, said maintaining means and said ignition means, said device comprising a member responsive to conditions of combustion in said combustion chamber, a first switch operable by said member for controlling the energization of said closing means and said ignition means and a second switch operable by said member for controlling the energization of said maintaining means, said first switch being closed when said member is relatively cool and being arranged to operate more slowly than said second switch, and said. second switch being closed when said member I is relatively hot.

2. In a heating control system, in combination, a combustion chamber, means for supplying fuel thereto, an electric motor for operating said fuelsupplying means, electrically operable means for igniting the fuel supplied to said combustion chamber, a switch for controlling the energization of said motor, means for closing said motor switch, means for maintaining said motor switch closed," and a device for controlling said closing means, said maintaining means and said ignition means, said device comprising a member responsive to conditions of combustion in said combustion chamber, a first switch operable by said member for controlling the energization of said closing means and said ignition means and a second switch operable by said member for controlswitch, and saidsecond switch being closed when said member is relatively hot.

3. In a heating control system, in combination,

-a combustion chamber, means for supplying fuel thereto,an electric motor for operating said fuelsupplying means, electrically operable means for igniting the fuel supplied to said combustion chamber, a switch for controlling the energization of said motor, means for closing said motor switch, means for maintaining said motor switch closed, and a device for controlling said closing means, said maintaining means and said ignition means, said device comprising a member responsive to conditions of combustion in said combustionchamber, a first switch operable by said member for controlling the energization of said closing means and said ignition means, a second switch operable by said member for controlling the energization of said maintaining means, said first switch being closed when said member is relatively cool and being arranged to operate more slowly than said second switch, and said second switch being closed when said member is relatively hot, and separate frictional slip connecting means between said member and said first and second switches.

4. In a heating control system, in combination,

a combustion chamber; means for supplying fuel thereto, an electric motor for operating said fuelsupplying means, electrically operable means for igniting the fuel supplied to said combustion chamber, a switch fof controlling the energization of said motonmeans for closing said motor switch, means for maintaining said motor switch closed, and a device for controlling said closing means, said maintaining means and said ignition means, said device comprising a member responsive to conditions of combustion in said combustion chamber, a first switch operable by said member for controlling the energization of said closing means and said ignition means, a second switch operableby said member for controlling the energization of said maintaining means, said first switch being closed when said member is relatively-cool and being constituted by a mercuryelectric contactor having a container of curved or humped formation to render the operation thereof slower than that of said second switch, and said second switch being closed when said member is relatively hot, and separate frictional slip connecting means between said'member and said first and second switches.

5. In a heating control system, in combination, a combustion chamber, means for supplying fuel thereto, an electric motor for operating said fuel-supplying means, electrically operable means for igniting the fuel suppl'ed to said combustion chamber, a switch for controlling the energization of-said motor, means for closing said motor switch, means for maintaining said motor switch closed, time-limit cut-out means connected in circuit with said closing means,

and a device for controlling saidclosing means, said maintaining means, said time -limit cut-out means, and said ignition means, said device coming means, said firstswitch being closed when said member is relatively cool and being arranged to operate more slowly than said second switch, and said second switch being closed when said member is relatively hot.

, 6. In a heating control system, in combination, a combustion chamber, means for supplying fuel thereto, an electric motor for operating said fuel-supplying means, electrically operable means for igniting the fuel supplied to said. combustion chamber, a switch for controlling theenergizaton of said motor, means for closing said motor switch, means for maintaining said motor switch closed, time-limit cut-out means connected in circuit with said closing means, and a device for controlling said closing means, said maintaining means, said time-limit cut-out means and said ignition means, said device comprising a member responsive to conditions of combustion in said combustion chamber, a first switch operable by said member for controlling the energization of said closing means, said time-limit cutout means, and said ignition means, and a second switch operable by said member for controlling the energization of said maintaining means, said first switch being closed when said member is relatively cool and being'co'nstituted by a merc'ury-electric 'contactor having a container of curved or humped formation to render the operation thereof slower than that of said secondswitch, and said second switch being closed when said member is relatively hot.

7. In a heating control system, in combination, a combustion chamber, means for. supplying fuel thereto, an electric motor for' operating said fuel-supplying means, electrically operable means for igniting the fuel supplied -to said combustion chamber, a switch for controlling the energization of said motor, means for closing said motor switch, means for maintaining said motor switch closed, time-limit cut-out means connected in circuit with said closing means, and a device for controlling said closing means, said maintaining means, said time-limit cut-out means and said ignition means, said device comprising a member responsive to conditions of combustion in said combustion chamber,

a first switch operable by saidmember for controlling the energization of said closing means, said time-limit cut-out means and said ignition means, a second switch operable by said member for controlling the energization of said maintaining means, said first switch being closed a when said member is relatively cool and being arranged to operate more slowly than said second switch, and ,said second switch being closed when said memberis relatively hot, and separate frictional slip connecting means between said member and said first and second switches.

8. In a heating control system, in combination, a combustion chamber, means forsupplying fuel thereto, an electric motor for operating said fuel-supplying means, electrically operable meansforigniting thefuelsimpliedtosaidcombustion chamber, a switch for the energization of said motor, means for closing said motor switch, means for maintaining said motor.

switch closed, time-limit cut-out means connected in circuit with said closing means, and a device for controlling said closing means, said maintaining means, said time-limit cut-out means and said ignition means, said device comprising a member responsive to conditions of combustion in said combustion chamber, a first switch operable by said member for controlling the energization of said closing means, said time-limit cut-out means, and said ignition means, a second switch operable by said member for controlling the energization of said maintaining means, said first switch being closed when said member is relatively cool and being constituted by a mercury-electric contactor having a container of curved or humped formation to render the operation thereof slower than that of said second switch, and said second switch being closed when said member is relatively hot, and separate frictional slip connecting means between said member and said first and second switches.

9. In a heating control system, in combinaling means to supply fuel to' the combustion chamber when said circuits are energized in accordance with normal conditions and to interrupt the supply of fuel for an interval if combustion falls during the supplying of fuel to the combustion chamber.

10. In a heating control system, in combination, a combustion chamber, electrical means for. controlling the supply of fuel thereto, a first circuit and a second circuit, a thermostatic device responsive to the presence or absence of combustion, switching mechanism controlled thereby for closing the second circuit prior to opening of the first circuit on the establishment of combustion and for. opening the second circuit substantially immediately and delaying reclosure of the first circuit upon a failure of combustion, and means controlled by the first and second circuits for causing the fuel supply controllingmeans to supply fuel to the combustion chamber when said circuits are energized inaccordance with normal conditions and to interrupt the supply of fuel for an interval if combustion fails during the supplying of fuel to the combustion chamber.

11. In a heating control system, in combinathermostat, and connections between the relay till means, nrst and second circuits and room thermostat.

12. A system of the class described, comprising,

in combination, a combustion chamber, electrical means for controlling the supply of fuel thereto, electrically operated ignition means, a first circuit and a second circuit, a device respomive to the presence or absence of combustion, switching mechanism controlled thereby for closing the second circuit prior to opening the first circuit upon the, establishment of combustion and for opening the second circuit before closing the first circuit upon failure of combustion, a thermostat subject to the temperature of the object to be heated, connections between the thermostat, ignition means, fuel supply controlling means and the first circuit of the switching mechanism for supplying fuel and igniting the same when said thermostat is cold, and connections between the fuel supply controlling means, thermostat, and the second circuit for continuing the supply of fuel and discontinuing ignition when combustion has been established whereby on failure of combustion the supply of fuel interrupted when the second circuit is opened cannot be resumed until the first circuit closed. I

13. A control system of the class described,

comprising, in combination, a combustion cham-= ber, electrical meansfor controlling the supply of fuel thereto, electrically operated ignition mearu for igniting the fuel supplied to the com bustion chamber, a thermostat responsive to the temperature of the object to be heated, a first circuit and a second circuit, a; combustion thermostat responsivev to the presence or absence of combustion,- switching mechanism operated thereby for closing the first circuit during absence of combustion, for closing the second cir cult prior to opening the first circuit when combustion is established, for substantially immediately opening the second circuit upon cessation of combustion and for reclosing the first circuit a delayed interval after the opening of the sec-- ond circuit, connections between the'roorn thermostat and first circuit for initiating operation of the fuel supply controlling means and ignition means when the thermostat becomes cold, and connections between the thermostat and the second circuit for continuing operation of the fuel supply controlling means only, upon opening of the first circuit as a result of the establishment of combustion.

14. A control system of the class described, comprising, in combination, a combustion chamber, electrical means for controlling the supply of fuel thereto, electrically operated ignition means, a thermostat responsive to the'temperature oi the object to be heated, a device responsive to the presence or absence of combustion, switching mechanism controlled thereby, a first circuit including the thermostat and switching mechanism for simultaneously operating the fuel supply controlling means and the ignition means when combustion is absent, a second circuit including the thermostat and switching mechanism which circuit is closed prior to opening of the first circuit when combustion is established for maintaining operation of the fuel supply controlling means only, said switching mechanism operating first to open the second circuit and subsequently to close the first circuit upon cessation of combustion, whereby, in the event of flame failure during operation of the system, the feeding of fuel to the combustion chamber is interrupted for a period of c after which the supply of fuel and operation of the ignition means therefor are resumed.

15. A system of the class described, comprising,

in combination, a combustion chamber, electrical means for controlling the supply of fuel thereto, an actuator responsive to the presence or absence of combustion, a switch, connections between the actuator and switch for moving the switch to open position as a result of a predetermined movement of the actuator in one direction upon establishment of combustion and for moving the switch to closed position as a result of a predetermined larger movement of the actuator in the opposite direction on cessation of combustion, an electro-thermal safety switch dominating the energization of the fuel supply controlling means, a circuit for energizing the electro-thermal safety switch including the cornbustioncontrolled switch, and means controlled by said actuator for interrupting the supply of fuel substantially immediately upon flame failure, Laid combustion controlled switch thereafter preventing reestablishment of combustion until it is reclosecl as a result of said predetermined larger movement of said actuator.

it. A system of the class described, compris ing, in combination, an electrical fuel supply controlling means, electrical ignition means to? igniting the fuel supplied by the fuel supply controlling means, an electro-thermal safety switch, a device responsive'to the presence or absence of combustion, switching mechanism, a first circuit and a second circuit controlled there= by, slip frictional means operatively connecting said combustion responsive device and said switching mechanism to close the second circuit and to open the first circuit substantially immediately upon the establishment of combustion and to open the second circuit substantially immediately but to delayclosing of the first circuit upon cessation of combustion, and means for initially energizing the fuel supply controlling means, ignition means and safety switch when the first circuit is closed and for maintaining energization of the fuel supply controlling means upon closure of the second circuit.

17. A system of the class described, comprising, in combination, fuel supplying means, an electric motor for operating said fuel supplying means, electrically operable means for igniting the fuel supplied by the fuel supplying means, an electro-thermal safety switch for rendering the system inoperative if combustion does not obtain within a predetermined time after the initiation of fuel supply, a thermostatic device responsive to the temperature of combustion, switching mechanism, a first circuit and a second circuit controlled thereby, slip frictional means operatively connecting said thermostatic device and said switching mechanism for substantially immediately closing the second circuit and opening the first circuit when the temperature of combustion rises and for substantially immediately opening the second circuit but delaying closing of the first circuit when the temperature of combustion falls, and means for ener izing the motor, ignition means and safety switch when the first circuit is closed, and for maintaining energization of the-motor when the second circuit is closed.

18. A system of the class described comprising an igniter, a fuel feeder, a safety timer for rendering the system inoperative if not de-energized at the endof a'predetermined time period, first its 7 means operative when energized for activating the igniter, fuel feeder and timer, second means operative when energized for continuing fuel feeder operation after ignition, first and second contacts and means for controlling them conformably to combustion conditions to have the first initially closed when a predetermined low temperature exists, to have the second close promptly on production of combustion, and have the first open at theend of a time period after the second closes, and circuits controlled by the contacts to permit energization of the first means while the first contact is closed, to obtain energization of the second means when the second contact closes, and to de-energize the first means on opening of the first contact, and on temperature fall due to combustion failure to delay closure of the first contact for atime period after the opening of the second contact.

19. A'system of the class described comprising an igniter, a fuel feeder, first means operative when energized for activating the igniter, and fuel feeder, second means operative when energized,

for continuing fuel feeder operation after ignition, first and second contacts and means for controlling them conformably to combustion conditions to have the first initially closed when a predetermined low temperature exists, to have the second close promptly on production of combustion, and have the first open at the end of a time period after the second closes, and circuits controlled by the contacts to permit energization of the first means while the first contact is closed, to obtain energization of the second means when the second contact closes, and to deenergize the first means on opening of the first contact, and on temperature fall due to combustion failure to delay closure of the first contact for a time period after opening of the second contact, I

20. A system of the class described comprising anigniter, a fuel feeder, first means operative when energized for activating the igniter and fuel feeder, second means operative when energized for continuing fuel feeder operation after ignition, a combustion responsive device having first and second contacts, and means for overlappingly controlling them on initial temperature 'rise to close the second before the first opens.

for non-overlappingly controlling them on temperature fall to close the first after the second opens, and circuits controlled by the contacts to permit energization of the first means while the first contact is closed, to obtain energization of the second means when the second contact closes, and'to de-energize the first means on opening of the first contact, and on temperature a fall due to combustion failure to first de-energize the second means and then permit energization of the first means.

21. A system of the class described, comprising, in combination,- a combustion chamber, means for controlling the supply of fuel thereto, a main control, a device having a predetermined range of movement in continuous response tochanges in combustion conditions; means under'the-control of said maincontrol and combustion condition responsive device upon a call'for heat during the absence of combustion for operating the fuel supply controlling means to supply fuel to the combustion chamber, and means under the control of said combustion condition responsive device for causing thefuel supply controlling means to terminate the supply of fuel to the combustion-chamber substantially immediately up n cessation of combustion while fuel is being supplied to the combustion chamber, said means operating to resume the supply of fuel to the combustion chamber after a time delay measured by changes in combustion conditions whereby any unconsumed vapors present in the combustion chamber may be discharged before the supply of fuel thereto is resumed.

22. A system of the class described, comprising, in combination, a combustion chamber, means for controlling the supply of fuel thereto, ignition means for igniting the fuel supplied to the combustion chamber, a main control, a device having a predetermined range of movement in continuous response to changes in combustion conditions, means under the control of said main control and combustion condition responsive device upon a call for heat during the absence of combustion for initiating operation of the fuel supply controlling means and ignition means, and means under the control of said, combustion condition responsive device for terminating operation of said ignition means and continuing operation of said fuel supply controlling means if combustion is established, said means operating to terminate the supply of fuel to the combustion cham-- ber substantially immediately upon cessation of combustion while fuel is being supplied thereto and then to restore operation of the ignition means and to resume the supply of fuel only after a time delay measured by operation of said combustion condition responsive device through said predetermined range of movement, whereby any unconsumed vapors in the combustion cham- I bet may be discharged'therefrom before the supply of fuel is resumed.

23. A system of the class described, comprising, in combination, electrically operated means for controlling the supply of fuel to a burner, an actuator responsive to combustion temperature, switching'mechanism controlled thereby including a switch which opens upon an increase in the temperature of combustion and closes only after a predetermined decrease in the temperature of combustion, a main switch, circuit connections controlled by the main switch and said switch of the combustion temperature responsive switchin combination, electrically operated means for controlling the supplyof fuel to a burner, an actuator responsive to (combustion temperature, switching mechanism controlled thereby including'a'swltch which opens upon an increase in the temperature of combustion and closes only after a predetermined decrease in the temperature of combustion, slip friction connecting means between said switch and said actuator, a main switch, circuit connections controlled by the main switch and said switch of the combustion temperature responsive switching mechanism for operating said fuel supply controlling means to supply fuel to the burner upon a deiii") neoaocv mend for heat, and circuit connections controlled by said combustion temperature responsive switching mechanism for effecting termination of the supply of fuel to the burner substantially immediately upon a dame failure during a demand for heat and effecting resumption of the supply of fuel upon reclosure of said switch of the combustion temperature responsive switching mechanism as the result of lowering of the combustion temperature said predetermined amount.

25. A system of the class described, comprising, in combination, an electrically operated fuel control device, ignition means for igniting the fuel, a main switch, a device responsive to combustion conditions of the fuel, a first switch, a second switch, means associated with the combustion responsive device and said first and second switches to open the first switch while the second switch is closed upon the establishment of combustion and to open the second switch a substantial time 'mterval before closing the first switch upon cessation of combustion, and means controlled by the main switch, first switch, and second switch for initiating and maintaining operation of the fuel control device under normal conditions, opening of said second switch on a failure of combustion after the same has been normally established causing said means to discontinue operation of the'fuel control device until reclosing of the first switch.

26. A system of the class described, comprising, in combination, an electrically operated fuel control device, ignition means for igniting the fuel, a main switch, a device responsive to combustion conditions of the fuel, a first switch, a second switch, means associated with the combustion responsive device and said first and second switches to open the first switch while the second switch is closed upon the establishment of combustion and to open the second switch a substantial time interval before closing the first switch upon cessation of combustion, and means controlled by the main switch, first switch, and second switch for initiating operation of the fuel control device and ignition means and maintaining operation of the fuel control device upon the successful establishment of combustion, opening of said second switch on a failure of combustion after the same has been normally established causing said means to discontinueoperation of the fuel control device until reclosure of the first switch whereupon the fuel control device and ignitionmeans are again operated to re-establish combustion...

27. A system of the class described, comprising, in combination, an electrically operated fuel control device, ignition means for igniting the fuel, safety timing means for terminating operation of the system, a main switch, a device responsive to combustion conditions of the fuel, a first switch, a second switch, means associated with the combustion responsive device' and said first and second switches to open the first switch while the second switch is' closed upon the establishment of combustion and to open the second switch a substantial time interval before closingthefirst switch upon cessation of combustion, and means controlled by the main switch, first switch, and

second switch for initiating operation of the fuel control device, ignition means and safety timing means to establish combustion and for maintaim ing operation of the fuelcontrol device only if combustion is established, opening of said second switch on a failure of combustion after the same has been normally established causing said means to discontinue operation of the fuel control device until reclosure of the first switch whereupon said fuel control device, ignition means and safety timing means are again operated in an attempt to reestablish combustion.

' 28. A system of the class described, comprising, in combination, electrical means for controlling the supply of fuel to a combustion chamber, an' actuator responsive to the presence or absence of combustion, a'first switch, connections between the actuator and first switch for moving the latter to open position as a result of a predetermined movement of the actuator in one direction upon the establishment of combustion and for moving the same to closed position as a result of a predetermined larger movement of the actuator in the reverse direction on cessation of combustion for any reason, electrical means for igniting the fuel supplied to the combustion chamber, an electrically operated safety timing means dominating operation of the system, circuit connections for energizing the fuel supply controlling means, igniting means, and safety timing means controlled by said first switch, a second switch controlled by said actuator for maintaining energization of the fuel supply controlling means only after said first switch has opened as a result of the establishment of combustion, and connections between said actuator and second switch for mov= ing the same to open position substantially immediately upon cessation of combustion, wherewill by, upon a failure of flame during normal operation, the supply of fuel to the combustion chamber will be substantially immediately interrupted and after a time delaymeasured by a predetermined movement of said actuator in response to the lowering of the temperature of combustion, said fuel supply controlling means, igniting means, and safety timing means will be re-energized in an attempt to re-establish combustion.

29. In combination, a burner motor, a motor switch, an actuator responsive to the temperature of combustion, means controlled by said actuator for maintaining said motor switch closed while combustion obtains but allowing said motor switch to open substantially immediately upon cessation of combustion due to a failure of flame, and means controlled by said actuator for effecting reclosure of said motor switch after movement of said actuator through a predetermined range upon lowering of the temperature of combustion due to such fiame failure.

30. In combination, a burner motor, a motor switch, a thermal actuator responsive to the temperature of combustion, means controlled by said actuator and including slip friction connecting means for maintaining said motor switch closed while combustion obtains but allowing said motor switch to open substantially immediately upon cessation of combustion due to a failure of flame, and means controlled by said actuator for efiecting reclosure of said motor switch after movement of said actuator through a predetermined range upon lowering of the temperature of coinbustion due to such a flame failure.

lilill 1 31. In combination, a burner motor, a motor ment of said actuator through a predetermined range upon lowering of the temperature of combustion due to such flame failure.

1 32. A system of the class described, compris-' ing, in-coinbination, an electrically operated fuel control device, ignition means for igniting the I fuel, a main switch, a device responsive to the establishing combustion, said second switch maintaining operation of the fuel control device only after the first switch opens upon establishment of combustion, whereby on a failure of combustion after successful establishment of the same, a delay is interposed before the fuel control device and ignition means can again be operated to reestablish combustion.

33; A system of the class described, comprising', in combination, an electrically operated fuel control device, ignition means for igniting the fuel, safety timing means for terminating operation of the system if combustion is not established within'a predetermined time, a main switch, a deviceresponsive to the temperature of combustion, a first switch controlled thereby, which switch is closed when combustion is absent, is opened substantially immediately when combustion is initially established and is reclosed a delayed interval after the cessation of combustion, a second switch controlled by the combustion responsive device, which second switch is opened substantially immediately upon cessation of combustion and is in closed position before the first switch is opened, and means under the control of said main switch and said first switch for initiating operation of the fuel control device, ignition means and safety timing means for establishing combustion, said means being controlled by said second switch for maintaining operation of the fuel control device only to maintain combustion after the first switch opens, whereby on a failure of combustion after successful establishment of the same, a delay is interposed before the fuel control device, ignition means and safety timing means can again be operated in an attempt to re-establish combustion.

HENRY F. DEVER. 

